Incandescent electric lamp



Feb. 13, 1945.

J. W. MARDEN ETAL INCANDE'SCENT ELECTRIC LAMP Filed Nov- 13, 1956 INVENTOR J'- w. mmmzw @ME/JMW.

ATTORNEY Patented Feb. 13, 1945 2,309,591 r 7 mcannsscasr anaemic ram John W. Mai-den, East Orange, and George Meister, Newark, N. -J., assignors to Westinghouse Electric 8: Manufacturing Company, East Pittsburgh, Pa a corporation of Pennsylvania V V 13 Claims.

This invention relates to incandescent electric lamps and more particularly to one having a coiled filament normally operating in an at,-

mosphere consisting principally of mercury vapor.

Many years ago mercury was proposed as a gas filling for lamps.

Attempts to use. it failed be- Application November 1a, 1936, Serial No. 110,584

n additional object of our invention is the provision of a novel method of making an incandescent electriclamp, including the introductionof a measured quantity of mercury into cause when such a lamp was used on constant voltage the filament had to be excessively heated while the mercury was being vaporized to produce the required pressure for protecting the filament.

After moisture is eliminated from a lamp bulb so that the enclosed filament is not destroyed by chemical action, the life of the filament is dependent on the rate of evaporation therefrom.

Gases suppress evaporation, but also tend to cool the filament. In lamps having filaments of the larger sizes, especially coils, the gain in light by reason of the higher temperatures which can be used in an inert gas, such as nitrogen, for ex ample, exceed the losses due to cooling, and the gas-filled lamp is more eflicient than that of the vacuum impe. Mercury vapor is more desirable as a filling than nitrogen, due to the poorer heat conductivity of this metal vapor.

with the foregoing consideration in mind, it is an object of our invention to produce an electric lamp comprising an incandescent filament operating in an atmosphere consisting mainly of mercury vapor.

Another object of our invention is the provision of an incandescent electric lamp of the gas type, in which the gas filling is normally substantially replaced by mercuryvapor.

A further object of our invention is the provision of an electric lamp comprising an envelope enclosing afilament surrounded by inert gas and containing mercury, so that when the filament is operated at incandescence, the gas filling will protect it ,from excessive vaporization until the mercury is vaporized suiiiciently to accomplish that Purpose. f

- A still further object of our invention is to provide an electric lamp in which a coiled filament initially operates in an atmosphere of inert' gas until mercury, included inthe bulb, is sufilciently vaporimd to such a pressure that its elect substantially replaces that of said gas" as a protective medium against excessive vaporization of the filament, and allow said filament to the bulb thereof, said mercury being a small.

amount so measured thatfit 'is completely vaporized during normal lamp operation.

Other objects and advantages of the invention relating'to the particular arrangement and construction of various parts will become apparent as the descriptionproceeds.

Referring to the drawing illustrating our invention, the scope whereof is defined by the appended claims:

Fig. 1 is a vertical sectional view of a lamp embodying 'our invention, portions thereof being illustrated in elevation;

Fig. 2 is a transverse sectional view on the line II1I.oif Fig. 1, in the direction of the arrows,

ortions being illustrated in elevation and parts broken away;

3 is a vertical sectional view, with parts in elevation, of another embodiment of our invention;

bodiment of our invention;

Fig. 5 is an elevational view of a still further embodiment of our invention;

' Fig. 6 is a diagrammatic view showing the characteristics of a choke coil which may be employed'with the embodiment of Fig. 5;

Fig. '7 is an elevational view illustrating apparatus which may be employed in introducing a small'measured quantity of mercury into a lamp bulb; and 1 Fig. 8 is a fragmentary view of a modified form of apparatus, such as shown in Fig. 7.

Referring to the drawing in detail, like parts bingdesignated by like referencecharacters,

and first considering the embodiment of our in-- vention illustrated in Figs. 1 and 2, there is shown a lamp I0 comprising a relatively small mercury-enclosinghard glass bulb ii, allowing for operation at a temperature high enough to keep a small quantity of mercury l9 completely vaporized, having a press l2, through which leads trated or coiled filament l5. Said'filament is' l3 and I extend and are connected to a concenpreferably formed of tungsten and positioned near, but below, the center of the bulb, so that the latter-is heated as uniformly as possible. I The operate at an efilcimcy higher than usual, be-

' cause it is anmundcd'hy' a medium of heat conductlvity poorer than the usual surrounding mefilament. of the present embodiment, is so mounted. that it takes the. form of a W .in elevation, as shown in Fig. 1, being curved'in' plan, as shown most clearly in Fig. 2. In order to hold the fila- Fig. .4 is an elevational view of a further emfilament, as illustrated. The press i2 is desirably of the "inverted," external, or "non-re-" entrant" type illustrated, so as to avoid cold pockets in which some of the mercury would condense.

Disposed in the bulb II is a small quantity of mercury l9, desirably measured so that all will be vaporized during normal operation of the lamp, to produce an operating pressure of from onehalf to about one atmosphere. By using a small, completely vaporizable amount of mercury, rather than a surplus, excessive mercury pressure, short circuiting or the coils by droplets, and interference with the transmission of light through the bulb by condensed vapor, are avoided. as superheatlng occurs after complete vaporization. in a given lamp will, of course, depend on the volume of the envelope and the normal or usual. running or operating lamp temperature. It may be introduced into the bulb, durin the operation of manufacturing the lamp, in any one of various ways, a preferred apparatus for the purpose becapillary tube 22 connecting with a vessel 23 containing mercury 24.

' The vessel 23 is likewise connected to a twoway stop cock 25 by means of a tube 26 so that it may be alternatively connected to a vacuum pump by means of a tube 21, or to the atmosphere by means of a tube or air inlet 28. The stop cock 2! has a tube 29 comprising a capillary portion graduated, as indicated at 30, and connected to the vacuum pump, like the tube 21.

The bulb H has the leads I! and II, sealed in as free from oxide as possible, it being pointed out that impure gas, moisture, badly oxidized leads, and oxidized filaments result in discolored lamps. The lamp is baked and gas-filled in the regular manner. In this case the gas may be introduced into the bulb at the proper time by means of a gas inlet, not shown, connecting with the tube 29, so that when the lamp is first operated, and before the mercury is substantially vaporized, there will be a protective atmosphere surrounding the filament.

When it is desir d to introduce the mercury, the stop cock 2i is turned to the position illustrated in Fig. 7, and the stop cook 25 slowly opened to allow air to enter and force the mercury up until it reaches the height indicated by X. which represents the desired measured quantitiy of mercury to be inserted in the bulb; The connection of the tube 29 with the vacuum pump causes the mercury to rise to the indicated level. The desired level can be accurately controlled by manipulating the stop cook 25, as it will be appreciated that turning the stop cock handle, so that the tube 28 is connected to the vacuum pump, results in lowering the mercury in the into the bulb ll of the lamp Ill, before or during The exact amount of mercury used- Ill the time the gas nlling is introduced. A preferred gas filling consists of a mixture of 86% argon and 14% nitrogen, by volume, at a pressure of about 150 millimeters of mercury. Other fillings inert to the tungsten filament, and having similar heat dissipating properties, may be satisfactorily employed; for example, a mixture of 77% helium and 23% nitrogen, by volume, at a pressure of about 65 millimeters of mercury.

Fig. 8 illustrates an alternative embodiment of the apparatus illustrated in Fig. 7, in which a bypass tube 3| with a stop cock 32 serves to directly connect the tube 29 with the tube 20", thereby facilitating the exhausting operation by making it unnecessary for the gas in the bulb II' to pass through the capillary portions of the tubes 29 and 20, and the stop cock 2|.

Alternative means of introducing mercury include placing small tubes of mercury in the bulb exhaust tube, which tubes are broken after removing from the pump and the mercury run or distilled into the bulb. Also, mercury may be distilled from a side tube into the bulb, or applied to the filament like a getter as a decomposable mercury compound. However, we prefer the introduction of the mercury as described in connection with Fig. '7 or Fig. 8.

Alternative forms of lamps are illustrated in Figs. 3, 4, and 5. In Fig. 3. a lamp iii is illustrated having a generally cylindrical bulb ii with a pair of presses 12. At one end a press i2 receives the lead It and at the other another press receives the lead II, to which leads are connected the normally vertical coiled-coil filament l5.

Fig. 4 illustrates an embodiment of our invention similar to Fig. 3, except that the bulb ii is generally frusto-conical with the small end down, rather than cylindrical as in Fig. 3, but. like the embodiment oi. that figure, also preferably contains a coiled-coil filament designated by the reference character l5". In the forms of both Figs. 3 and 4, a measured quantity of mercury is included, as designated by the reference character I9 in Fig. 3, and a filling of gas such as described in connection with Figs. 1 and 2. The advantage of the inverted generally-conical form of bulb, illustrated in Fig. 4, is that the temperature is maintained at greater uniformity, as the bulb wall in the hotter portion thereof is farther from the filament. In both of these forms, the presses are desirably covered with a fireproof insulating material, such as asbestos, designated by the reference character 33, in Fig. 3 and 33 inFlg. 4.

Referring now to the embodiment of our invention illustrated in Fig. 5, we have a lamp it comprising an envelope l l and enclosing a preferably coiled or concentrated filament i5-,

connected with lead wires 13 and I4 extending through a Dress I2, and disposed in a fairly high vacuum, for example,- such as in an inert gas, argon, or neon, at a pressure substantially lower than that of the preceding embodiments, such for example as that of from about ten to fifty millimeters of mercury. A measured quantity of mercury l9 is enclosed in the bulb, as in the previous embodiments.

The lamp of Fig. 5 is provided with arcing points 94 and 35 and designed for use with a choke coil or other device having the characteristics illustrated in Fig. 6, in order to protect the filament until the mercury vapor pressure builds up sumciently for that purpose.

When the lamp is first turned on, an arc breaks between the points 34 and SI and the lamp runs at low voltage, for example, 20 volts,

as indicated in the diagram in Fig. 6, until the is connected to the lamp and allowed to flow thereto.

3. An electric lamp comprising an envelope, an incandescible filament disposed therein and supported-from leads. and arcing points extending from said leads into close proximity to one another, said envelope containing mercury which during operation is adapted to form the main atmosphere surrounding the filament, a transparent outer casing enclosing said envelope, a

. base on said casing, lead-in conductors extendat least 90%.

In all the forms of our invention illustrated it is necessary to operate the lamp hot in order to maintain the required mercury vapor pressure,

which should be from one-half to about one atmosphere in order to suppress the vaporization of the tungsten to the desired extent. In order, therefore, to protect the bulb from air currents.

fixtures from overheating, and the user from burns, the lamps of all of our embodiments are desirably used with a housing It as shown in Figs. 1 and 2, and asbestos coverings on the presses, as illustrated in Figs. 3 and 4.

The housing 38 may comprise a glass envelope 3! receiving the lamp and protected by a disc 88, of mica or the like, through which the leads l3 and it pass for connection with a special base 39. The base 39 may have a threaded outer metal shell 40 forming one contact and separated i'roma central contact 4| by a glass or other insulative filling 42, from which an errla'rged portion 43 of the baseextends into embracing relationship with the peripheral portion of the'open end of the glass enclosing member ing from said base to said filament, and a disc through which said lead-in conductors extend,

disposed in said outer casing and. spaced from.

said base, in .order to protect it from over-heating during operation of said lamp.

4.'An electric lamp comprising a sealed glass envelope, an incandescible tungsten; filament. less than A of,an' atmosphere of an inert gas filling,

mercury'in said envelope and so small in quantity as compared with the volume of and usual runhing temperature in the envelope that it is com- 81, being desirably sealed thereto byicement or:

filament normally operates in an atmosphere consisting principally of completely vaporized mercury, or superheated mercury vapor, which has a relativelylow heat conductivity, compared with the inert gas usually employed as a filling.

thereby making it possible tooperate at higher efiiciency, or with smaller heat losses'un'der comparable conditions.

Although preferred embodiments of our in-' vention have been'disclosed, it will be understood that modifications may be made within the spirit and scope of the appended claims. 4

We claim:

1. An electric lamp comprisinga sealed glass envelope containing a tungsten filament, an inert gas filling and mercury, a transparent outer casing enclosing said envelope, a base on said casing. lead-in conductors extending from said base to said filament, and a disc through which said lead-in conductors extend, disposed in said outer casing, and spaced from said base, in order to protect'it from over-heating during operatic of said lamp. E.

2. The method of introducing a desired quantity of mercury into an electric lamp comprising,

connecting a reservoir of mercury through a two-way valve to said lamp and a vacuum pump, allowing said mercury to be drawn to a calibrated portion of a tube between said valve and pump, until a measured quantity is trapped by said valve, and turning said valve until said quantity pletely vaporized during normal operation of the lamp to produce a substantial protective mercury vapor pressure greater than that of said gas, a

' normal running temperature in theenvelopa'that it is completely vaporized to produce. an operating pressure of from one-half to about one atmosphere during normal operation of the lamp, a

transparent outer casing enclosing said envelope, a base on said casing, lead-in conductors extending from said base to said filament, and a disc through which said lead-in conductors extend, disposed in said outer casing and spaced from said base, in order to protect it from over-heating during operation of said lamp.

6. An electric lamp comprising a sealed enve- "lope containing a tungsten filament, an inert gaseous filling, and mercury so small in quantity, as compared with the volume of and usual running temperature in the envelope, that it is completely vaporized during normal operation of the lamp to produce a substantial protective mercury vapor pressure, said envelope being substantially frusto-conical, the filament [disposed substantially co-axial therewith, and said lamp being adapted for operation with the large end uppermost, in order to insure more nearly uniform temperature conditions in the envelope, a transparent outer casing enclosing said envelope, a base on said casing and disposed .adjacent the large end of said envelope, lead-in conductors extending from said base to said filament, and a disc through which said lead-in conductors extend. disposed in said outer casing and spaced from said base, in order to protect it from overgaseous filling at a ressure of about one hundred and fifty millimeters, a measured amount of mercury in said envelope and so small in quantity,

"as compared with the volume oi and usual running temperature in the envelope. that it is completely vaporized during normal operation of the lamp to produce a pressure of more than one half an atmosphere, a transparent outer casing enclosing said envelope, a base on said casing,

' lead-in conductors extending from said base to cent argon and about fourteen percent nitrogen and at a pressure of about one hundred and fifty millimeters of mercury, mercury in said envelope and so small in quantity that it is completely vaporized during normal operation of the lamp to produce an operating pressure of from one-halt to one atmosphere, a transparent outer casing enclosing said envelope, a base on said casing, lead-in conductors extending from said base to said filament, and a disc through which said leadin conductors extend, disposed in said outer casing and spaced from said base; in order to pro- {act it from over-heating during operation of said amp.

9. An electric lamp comprising a sealed envelope, a tungsten filament mounted therein, a gaseous filling consisting of about seventy-seven percent helium and about twenty-three percent nitrogen and at a pressure of about sixty-five millimeters of mercury, mercury in said envelope and so small in quantity that it is completely vaporized during normal operation of the lamp to produce an operating pressure of from onehalf to one atmosphere, a transparent outer casing enclosing said envelope, a base on said casing, lead-in conductors extending form said base to said filament, and a disc through which said lead-in conductors extend. disposed in said outer casing and spaced from said base, in order to protect it from over-heating during operation of said lamp.

10. An incandescent electric lamp comprising a translucent envelope of high melting point vit reous material having a filament mounted therein and containing a quantity of mercury and a filling ofan inert gas, the amount of mercury being such that at the operating temperature of the lamp it is completely vaporized and the pressure of the mercury vapor lies between onehalf and one atmosphere, a transparent outer casing enclosing said envelope, a base on said casing, lead-in conductors extending from said base to said filament, and a disc through which said lead-in conductors extend, disposed in said outer casing and spaced from said base, in order said leads into close proximity to one another, inert gas at low pressure in said envelope and surrounding said leads and points, a quantity of mercury in said envelope, and means for applying such electrical powerto said leads and so conserving the heat developed in the envelope that first an arc breaks between said points and the lamp runs at reduced voltage with little heat in the filament, then the mercury in the envelope is vaporized by the heat from the arc, builds up a relatively high pressure of mercury vapor and quenches the arc, causing the full voltage to be impressed on the filament, and then the filament operates at desired incandescence in the heat-,

developed atmosphere consisting mainly of marcur vapor.

12. An incandescent filament electric lamp with an auxiliary discharge starting device comprising an enclosing envelope, leads and an incandescible filament supported therefrom and disposed therein, arcing points extending from said leads into close proximity to one another. inert gas as a pressure of from about ten to fifty millimeters of mercury in said envelope and surrounding said leads and points, a quantity of mercury disposed in said envelope and measured so that it is completely vaporized during lamp operation, a ballast device connected in series with said lead-in conductors, and power means for so operating said lamp through said ballast that first an arc breaks between said points, because of the initial low pressure of the surrounding gas, and the lamp runs on a relatively high current at reduced voltage, the heat of said arc then vaporizes the mercury building up the pressure thereof so high that said arc is extinguished, whereupon said filament then operates on full voltage at the desired temperature in the heatdeveloped and maintained protective atmosphere consisting mainly of mercury vapor.

13. The method of operating an incandescent filament electric lamp having an auxiliary discharge starting device; which lamp comprises an enclosing envelope containing mercury and having leads, an incandescible filament supported from said leads and disposed in said envelope, arcing points extending from said leads into close proximity to one another, and an inert gas filling at a starting pressure of from about ten to fifty millimeters of mercury; comprising applying electric power of such a character to said leads that. first, an arc breaks between said points, because of the initial low pressure of the gas filling, and the lamp runs on a relatively high current at reduced voltage, with the heat of the arc vaporizing'the mercury and building up a pressure to protect it from over-heating during operation of said lamp.

11. An incandescent filament electric lamp with an auxiliary discharge starting device comprising an enclosing envelope, leads and an incandescible filament supported therefrom and disposed therein, arcing points extending from thereof, second, extinguishing the are by said pressure of the mercury and, then, operating the filament on full voltage at the desired temperature in the protective atmosphere consisting mainly of the mercury vapor which was developed and maintained by the heat of operation.

JOHN W. MARDEN. GEORGE MEISTER. 

